We are talking about a cloak that really and truly renders the wearer completely invisible, and endures eternally, giving constant and impenetrable concealment, no matter what spells are cast at it.

The Cloak was exactly what Xenophilius had described: A cloak that really and truly renders the wearer completely invisible, and endures eternally, giving constant and impenetrable concealment, no matter what spells are cast at itů And then, with a gasp, he remembered — "Dumbledore had my Cloak the night my parents died!"